1. Field of the Invention
The present invention relates to telephony. In particular, the present invention relates to concealing the mute function in an IP-based telephony system.
2. The Prior Art
The widespread acceptance and use of the Internet has generated much excitement, particularly among those who see the Internet as a possible substitute for the traditional telephone system. As the backbone of the Internet continues to be upgraded and expanded, the promise of a low-cost substitute to the traditional PBX system may now be realized.
One type of Internet-based telephony system that is gaining acceptance is IP telephony, which transfers voice information over the Internet Protocol (IP) of the TCP/IP protocol suite. While many standards exist, such as Voice over Packet (VOP) for Frame Relay and ATM networks, as used herein the term xe2x80x9cIP telephonyxe2x80x9d will be used to designate voice over any packet-based network. In IP telephony, a user wishing to communicate uses an IP telephone, which is a device which transports voice over a network using data packets instead of the traditional switched circuits of a voice only network.
FIG. 1 shows an IP telephony system 100 of the prior art. System 100 includes a business system 102 configured to provide IP telephony in an enterprise environment. Business system 102 may include a network 104, such as a corporate Ethernet LAN, to which a plurality of IP telephones 106 may be operatively coupled to network 104 using hardware and software standard in the art. To couple the business system 102 to the outside world, typically a gateway 108 standard in the art is provided and operatively coupled between network 104 and backbone network 110.
Backbone network 110 may be any packet-based network standard in the art, such as IP, Frame Relay, or ATM. To provide voice communications to legacy POTS phones, typically a gateway 112 is provided, which may be a VoP gateway. Gateway 112 provides access to the Public Switched Telephone Network (PSTN) 114. Through PSTN 114, voice-only communications may be provided to legacy POTS phones 116.
The system 100 of FIG. 1 also includes an example of a broadband residential system 118. To reach individual residences, typically local ISP providers provide a cable or DSL head end 120 standard in the art. An individual wishing to utilize the ISP""s service may then employ a cable modem or DSL modem 122 coupled to the user""s home LAN 124. The user""s home LAN may be provided by a home PC 126 configured to run software standard in the art such Microsoft Windows(copyright). The user may then operatively couple an IP telephone 128 to the LAN 124.
Thus, in the system 100 of FIG. 1, IP telephones 106 in business system 102 may communicate by voice with other similar business systems similarly configured with IP telephones. For a business enterprise, communication by IP telephony may be advantageous because the need for a traditional PBX system can be eliminated. Furthermore, an IP telephony system is scalable and may be upgraded along with the enterprise""s network system.
Likewise, the residence of system 118 may communicate by voice to a POTS phone 116 using IP telephone 128. From the view of the home user, the communication of FIG. 1 is advantageous because the communication operates over the backbone network 110 without accessing traditional long-distance service providers.
FIG. 2 is conceptual block diagram of a prior art IP telephone system 200 including a TX unit 202 of a transmitting IP telephone standard in the art and a RX unit 204 of a receiving IP telephone standard in the art. TX unit 202 and RX unit 204 are shown operatively coupled to each other through a network cloud 216. For the sake of clarity, elements of a typical IP telephone not essential to the explanation of the present invention are not shown in the disclosure.
TX unit 202 includes a microphone 206 coupled to a mute switch 207. The mute switch is toggled by a mute user input 227 which may consist of a physical button or softkey on the IP telephone. Mute switch 207 couples the input audio stream to a Voice Activity Detector (VAD) 208, a silence indication packet generator 212 and an encoder 214. VAD 208, encoder 214, and silence indication packet source 212 are operatively coupled to each other to provide an output for transmission over network 216.
In a typical operation, voice information is received on microphone 206 and presented to mute switch 207. If the mute function of the IP telephone is not engaged through the mute user input 227 (i.e., the mute is off) the mute switch 207 will be closed, and the voice information will be presented to the VAD 208, the encoder and the silence indication packet source 212.
Using methods known in the art, the VAD 208 will determine whether there is voice activity present in the signal coming from microphone 206. If there is voice activity in the signal, the switching logic will pass the output of the encoder (i.e., a packet stream) for transmission to network cloud 216 using methods standard in the art.
If the VAD 208 determines that there is no voice activity present on the signal coming from microphone 206, then the switching logic 210 will send one or more silence indications packets to network cloud 116. The silence indication packets contain at least a background noise level so that the comfort noise generator 218 on the receive side can generate noise similar in level and character to the actual background noise on the transmit side.
As is known by those skilled in the art, in some IP telephony systems, a user may disable the VAD of their IP telephone. In such a situation, only background noise can be sent, since silence indication packets can no longer be sent. As used herein, background noise will be used to designate either real background noise, or comfort noise, depending on how the IP telephone is configured.
Comfort noise is a prior art solution to save network bandwidth. The prior art methods determined that if there is no voice activity present, then no voice packets should be sent over the network. However, this results in a unnatural silence appearing on the receiving unit, since no packets are being sent. As a result, the prior art methods developed the concept of comfort noise, which presents the listener with generated noise designed to mimic the line noise of traditional legacy telephones when there is no voice activity present. The comfort noise reassures listeners that their connection is still active.
Referring still to FIG. 2, RX unit 204 includes a comfort noise generator 218 operatively coupled to a decoder 220. The comfort noise generator 218 and decoder 220 are both operatively coupled to switching logic 224. When the output of TX unit 202 has been transmitted over network 216, it will be received by RX unit 204, and presented to a decoder 220 and a comfort noise generator 218 using methods standard in the art.
If the switching logic receives an encoded voice packet it routes it to the decoder which then outputs the decoded audio signal tot the speaker 226. If the switching logic receives a silence indication packet it routes it the comfort noise generator 218 which then generates comfort noise to the speaker 226 until further voice packets are received. Typically, the CF comprises white or pink noise.
While the systems of FIGS. 1 and 2 perform well for there intended purpose, some disadvantages have been encountered when compared to legacy phone systems. For example, some users of IP telephones have reported inconveniences when using the mute function of an IP telephone.
Referring back to FIG. 2, when the mute function is engaged (i.e., the mute is turned on), mute switch 207 will be open. In prior art systems, the switching logic 210 will sense the opening of mute switch 207, and cease to send voice packets or CF packets over the network. Thus, no information will be transmitted over the network, resulting in silence appearing on the receiving unit. Switching logic 210 may also send CF packets which contain pure silence indication due to the opening of switch 207. Since this silence does not have any voice information or CF noise present, listeners may perceive that the line has gone dead or that they have been disconnected.
FIG. 3 is a prior art conceptual diagram showing IP telephony data flow received by a receiving unit when the mute function is engaged on a transmitting unit. The blocks of FIG. 3 represents the information present during time intervals T1 through T5.
In time interval T1, the receiving unit may be receiving voice information while engaging in a conversation. When the conversation quiets down, the receiving unit may then receive background noise in time interval T2. If the transmitting parties engage the mute function of the transmitting unit, the receiving unit will then hear the background noise disappear and be replaced by silence during time interval T3. After the transmitting party disengages the mute function of the transmitting unit in time interval T4, background noise will reappear. Finally, the conversation may resume in time interval 5, and the receiving unit will again hear voice information. Thus, the listening parties utilizing IP telephones of the prior art will perceive silence when the transmitting parties engage the mute function of their IP telephones. This interval of silence has certain disadvantages, including the perception by the receiving party that the connection has been lost, as well as the uncomfortable feeling the results from knowing the other party is censoring the conversation.
Hence there is a need for a method and apparatus to eliminate the silence that occurs when the mute function of an IP telephone is engaged.
The invention satisfies the above needs. The present invention relates to telephony. In particular, the present invention relates to concealing the mute function in an IP-based telephony system.
A method and apparatus for improving the mute function of an IP telephone is disclosed, where the method comprises determining, by a transmitting IP telephone, whether the mute function has been activated; and if the mute function has been activated, then providing, a predetermined output.
Various aspects of the method are disclosed, including: an aspect where the predetermined output is characterized by the absence of silence as detected by an RX unit when the mute function of a TX unit is activated; an aspect where the predetermined output comprises a signal in which voice information has been removed; and an aspect where the removing of voice information is performed by an audio filter disposed within the TX unit of an IP telephone.
Additional aspects of the present invention is disclosed where the predetermined output is comfort noise, and where the act of providing comfort noise is performed by a mute switch disposed within the switching logic of a TX unit of an IP telephone.
By using IP telephones configured according to the present invention, listeners will not experience the silence which is heard in IP telephones of the prior art when the mute function is activated.